De Ravin was born in Mount Eliza, Victoria, Australia, an outer southeastern suburb of Melbourne. She has French ancestry, de Ravin means of (the) ravine in French. Having studied ballet since the age of nine at Christa Cameron School of Ballet in Melbourne, and being home schooled by her mother, she was accepted into the Australian Ballet School at fifteen. There, she performed in productions with The Australian Ballet as well as Danceworld 301. Ravin studied acting at Australia's National Institute of Dramatic Art, and with the Prime Time Actors Studio in Los Angeles.
De Ravin's first major role was a recurring part as Curupira in the TV series Beastmaster. She went on to appear as alien/human hybrid Tess Harding in the teen television series, Roswell. She landed this role one month after moving to Los Angeles at the age of 18. In 2004, de Ravin was cast to portray the role of Claire Littleton on the hit ABC drama Lost, co-written by the co-creators of Once Upon a Time, Edward Kitsis and Adam Horowitz. In answer to whether she expected the success of Lost, de Ravin said: "It's sort of hard to say. You read something and have a good feeling about it, it sounds great, ties nicely together and then shooting something, editing it, the music, the actors involved, everything sort of plays a huge part. Everyone involved had a great feeling towards it, but you never really know". De Ravin was a series regular for the first four seasons and for the sixth and final season.
In 2005, de Ravin was cast to portray the role of Emily Kostich, the heroin-addicted ex-girlfriend of Brendan Frye (Joseph Gordon-Levitt), in the neo-noir film Brick. In an interview about the film, Ravin told that she was attracted by the script because it was original and the teens in the film are very deep and emotional for their age. A year later, de Ravin had a lead role and was cast as Brenda Carter in the remake of The Hills Have Eyes. The film performed well at the box office. In 2007, Variety reported that she would be starring in the film Ball Don't Lie, which premiered at the 2008 Tribeca Film Festival, which arrived in cinemas early 2009. De Ravin was cast to appear in William Dear's The Perfect Game, and appeared in the 2009 film Public Enemies as a bank teller named Barbara Patzke.
De Ravin was cast in the movie adaption of the video game Onimusha, but due to producer Samuel Hadida's other project The Imaginarium of Doctor Parnassus, and star Heath Ledger's death, Hadida was forced to push back the release date of the film. Onimusha is postponed for an unknown amount of time and there is not any confirmation if de Ravin will continue the project.
In 2012, she started work on the American television series Once Upon a Time, in the role of Belle, from the famous tale of "Beauty and the Beast". She started out as a semi-recurring guest star in season 1 and was promoted to a series regular for season 2.
After three years of dating, actor Josh Janowicz proposed to de Ravin on New Year's Day 2005 in Melbourne, which she said "was very impromptu and very sweet". Ravin met Janowicz in Los Angeles, and said that "our life together always comes before work. You can't buy love or family." While filming Lost, de Ravin flew to and from Hawaii "once or twice a week" to return to her home in Burbank, California, which she shared with Janowicz and their poodle, Bella. The couple married 19 June 2006 in Melbourne, Australia. They separated 6 months after they married, and got back together. In June 2009, it was reported that they have been living separately and have filed for divorce. In October 2009, she called off the divorce after a trip to Japan with her husband. In July 2014, it was announced that they have separated again, having not lived together since November 2013.
On October 2nd, 2015, Emilie de Ravin confirmed that she was pregnant; Eric Bilitch is the father.